Report 1 - Research for Thermal of Products

7/16/2019 Report 1 - Research for Thermal of Products

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VIN KHOA HC V CNG NGH VIT NAM______________________________________

D nSn xut th nghim cc sn phm chiu sng hiu qu cao

BO CO CHUYN Nghin cu ch nhit ca MOSFET v hon thin ccgii php k thut gim nhit cho MOSFET trong b

ngun cho n LED cng sut di 100W

n v thc hin d nTrung tm H tr Pht trin Cng ngh vDch v (CTDAS), Vin Khoa hc v Cngngh Vit Nam (VAST)

H Ni, thng 6-2011


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VIN KHOA HC V CNG NGH VIT NAM_______________________________________

D nSn xut th nghim cc sn phm chiu sng hiu qu cao

BO CO KT QU S 1Nghin cu ch nhit ca MOSFET v hon thin ccgii php k thut gim nhit cho MOSFET trong b

ngun cho n LED cng sut di 100W

1. Thi gian thc hin: 11/2009 - 1/2010

2. Ngi thc hin:

STT

H v tn Hc hmHc v

n v cng tc Cng vic thc hin

123

4

Gim c CTDAS Trng nhm

TS. Nguyn Vn Thao TS. Nguyn Th Bc Kinh

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MC LC

1. Bng ch gii thut ng v cc ch vit tt

2. Lit k cc hnh3. Lit k bng biu4. Cc k hiu trong cng thc tnh5. Nhim v nghin cu6. Phm vi nghin cu7. Kho cu v MOSFET8. Cc gii php k thut ci thin ch nhit ca MOSFET9. Phng n xut10.Kt qu thc nghim

11.Kt lun12.Ti liu tham kho


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1. Bng ch gii thut ng v cc ch vit tt

TTThut ng

v cc ch vit tt Ch gii

1 MOSFET(Transistor) MOSFET vit tt ca "Metal-OxideSemiconductor Field-Effect Transistor-Transistor hiu ng trng bn dn oxit kim loi,l mt thut ng ch cc transistor hiu ngtrng c s dng rt ph bin trong cc mchs v cc mch tng t.

Transistor MOSFET c xy dng da trn lpchuyn tip Oxit Kim loi v bn dn ( v d OxitBc v bn dn Silic)

MOSFET c hai loi:

N-MOSFET: ch hot ng khi ngun in Input(Gate) l zero, cc electron bn trong vn tinhnh hot ng cho n khi b nh hng bingun in Input.

P-MOSFET: cc electron s b cut-off cho n khigia tng ngun in th vo

2 Dng drain The subthreshold drain current is the current

that flows between the source and drain of aMOSFET when the transistor is in subthresholdregion, orweak-inversion region, that is, for gate-to-source voltages below the threshold voltage.The subthreshold region is often referred to as theweak inversion region . The terminology forvarious degrees of inversion is described inTsividis.[1]

3 PWM Pulse-width modulation (PWM), orpulse-duration modulation (PDM), is a commonlyused technique for controlling power to inertial

electrical devices, made practical by modernelectronic power switches.

4 SMPS A switched-mode power supply (switching-mode power supply, SMPS, or simply switcher)is an electronicpower supply that incorporates aswitching regulator in order to be highly efficientin the conversion of electrical power.

5 JFET The junction gate field-effect transistor (JFETorJUGFET) is the simplest type offield effecttransistor. It can be used as an electronically-controlled switch or as a voltage-controlled
http://en.wikipedia.org/wiki/MOSFET#Modes_of_operationhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Threshold_voltagehttp://en.wikipedia.org/wiki/Subthreshold_conduction#cite_note-Tsividis-0http://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Field_effect_transistorhttp://en.wikipedia.org/wiki/Field_effect_transistorhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Switchhttp://en.wikipedia.org/wiki/MOSFET#Modes_of_operationhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Threshold_voltagehttp://en.wikipedia.org/wiki/Subthreshold_conduction#cite_note-Tsividis-0http://en.wikipedia.org/wiki/Power_supplyhttp://en.wikipedia.org/wiki/Field_effect_transistorhttp://en.wikipedia.org/wiki/Field_effect_transistorhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Switch


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resistance.Electric charge flows through asemiconducting channel between "source" and"drain" terminals. By applying a bias voltage to a"gate" terminal, the channel is "pinched", so thatthe electric current is impeded or switched off

completely.

Electric currentfromsource to drain in a p-channel JFET is restricted when a voltage isapplied to thegate.

6 BJTs The bipolar power junction transistors (BJTs)A bipolar (junction) transistor (BJT) is a three-terminal electronic device constructed ofdopedsemiconductormaterial and may be used inamplifying or switching applications.Bipolartransistors are so named because their operation

involves both electronsand holes. Charge flow ina BJT is due to bidirectional diffusion ofchargecarriers across a junction between two regions ofdifferent charge concentrations. This mode ofoperation is contrasted with unipolar transistors,such as field-effect transistors, in which only onecarrier type is involved in charge flow due todrift. By design, most of the BJT collector currentis due to the flow of charges injected from a high-concentration emitter into the base where they areminority carriersthat diffuse toward the collector,

and so BJTs are classified as minority-carrierdevices.

7 driftregion In the device we identify a driftregion, a large regionin the center of the device, and a tiny transitionregion, below the gate. Their respective geometriesdiffer a lot and as a result the models

5
http://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Doping_(Semiconductors)http://en.wikipedia.org/wiki/Doping_(Semiconductors)http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Charge_carriers_in_semiconductorshttp://en.wikipedia.org/wiki/Charge_carriers_in_semiconductorshttp://en.wikipedia.org/wiki/Field-effect_transistorhttp://en.wikipedia.org/wiki/Drift_velocityhttp://en.wikipedia.org/wiki/Minority_carrierhttp://en.wikipedia.org/wiki/Minority_carrierhttp://en.wikipedia.org/wiki/File:Jfet.pnghttp://en.wikipedia.org/wiki/File:Jfet.pnghttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Transistorhttp://en.wikipedia.org/wiki/Doping_(Semiconductors)http://en.wikipedia.org/wiki/Semiconductorhttp://en.wikipedia.org/wiki/Electronic_amplifierhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Charge_carriers_in_semiconductorshttp://en.wikipedia.org/wiki/Charge_carriers_in_semiconductorshttp://en.wikipedia.org/wiki/Field-effect_transistorhttp://en.wikipedia.org/wiki/Drift_velocityhttp://en.wikipedia.org/wiki/Minority_carrier


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for them differ as well.

8 FOT Fixed off-time (network)9 CCM

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2. Lit k cc hnh

Hnh 1 S nguyn l ca mt SMPS kiu FlybackHnh 2 S nguyn l ca mt SMPS kiu Buck

Hnh 3 Cu trc ca mt MOSFET knh N v k hiuHnh 4 (a) Mt ct ngang ng ca MOSFET cng sut; v

(b) Miu t dng n gin cu trc MOSFET11

Hnh 5 (a) Mt ct ngang ca mt MOSFET knh N; v(b) Cc phn t k sinh trong diode

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Hnh 6 Quan h gia in tr trng thi m RDS(on) v dng drain ID 13Hnh 7 Quan h gia RDS(on) v nhit lp tip xc Tj 13Hnh 8 Quan h RDS(on) v V(BR)DSS 14Hnh 9 (a) Diode ni ti trong; v

(b) Phng thc b xung mt diode phc hi nhanh

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Hnh 10 (a) M t cc in dung k sinh trong MOSFET; v(b) Miu t v tr vt l ca cc in dung k sinh

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Hnh 11 S ph thuc ca in tr drain-source vo dng drain (tiTj=25oC)

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Hnh 12 S ph thuc ca in tr diode vo dng diode 18Hnh 13 Xc nh gi tr RDSonMAX(25oC) t data-sheet 19Hnh 14 Xc nh TJ/RDSon t the data-sheet 19Hnh 15 Mch kim tra tn tht chuyn mch ca MOSFET 21Hnh 16 Qu chuyn mch trn MOSFET cng sut 22

Hnh 17


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3. Lit k bng biu

4. Cc k hiu trong cng thc ton hc

Pl Power lossesPc Conduction lossesPsw Switching lossesPb Blocking (leakage) losses

pCM Instantaneous value of the MOSFETconduction losses

PCM Average value of the MOSFET

conduction lossespCD Instantaneous value of the diode

conduction lossesPCM Average value of the diode

conduction lossesPswM MOSFET switching lossesPswD Diode switching lossesPM MOSFET lossesPD Diode lossesPo Converter output power

EonM MOSFET switch-on energyEonMi MOSFET switch-on energy withouttaking the reverse recovery processinto account

EonMrr MOSFET switch-on energy causedby the reverse-recovery of the free-wheeling diode

EonD Diode energy during MOSFETswitch-on transient

EoffM MOSFET switch-off energyuDS Drain-source voltage

uD Voltage across the diodeuD0 Diode on-state zero-current voltageUDr Driver output voltageUGS Gate-source voltageUGSth Gate-source threshold voltageU(plateau) Plateau voltageUDrr Voltage across the diode during

reverse recoveryUDD Converter supply (DC bus) voltageUin Converter input voltage

Uo Converter output voltage


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uL Voltage across the loadiD Drain currentIDrms RMS value of the drain currentiF Current through the diodeIfav Average diode current

IFrms RMS value of the diode currentIrr Reverse recovery currentIFrrpeak Peak value of the diode reverse

recovery currentIG Gate currentiL Load currentIin Converter input currentIo Converter output currentRDSon Drain source on-state resistanceRD Diode on-state resistance

RG Gate resistorCGS Gate-source capacitanceCGD Gate-drain capacitanceCDS Drain-source capacitanceQrr Reverse recovery chargeR Load resistor L Load InductanceTj Junction temperature Temperature coefficientTsw Switching periodfsw Switching frequencytri Current rise timetfi Current fall timetru Voltage rise timetfu Voltage fall timetrr Reverse recovery timeD Duty cycle

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5. Nhim v nghin cu

MOSFET l phn t c bn trong cc SMPS. Theo nguyn l hot ng trong ccSMPS, MOSFET phi m nhim chc nng ng ngt dng drain trong cc mchPWM v mch PFC, qu trnh ny lm tn hao mt cng sut Pl c gii phng ra

di dng nhit nng. Tn tht cng sut trong MOSFET l yu t ch yu lm gimhiu sut v tng nhit lm vic ca b ngun, qua nh hng ti hiu sut v n nh, tin cy ca cc SMPS.

Vic kim sot v khng ch nhit lm vic ca MOSFET di gii hn chophp trong qu trnh hot ng ca cc SMPS l nhim v quan trng trong qu trnhthit k cc SMPS ni ring v trong in t cng sut ni chung, c bit l trong ccSMPS cng sut ln. Tn tht trong MOSFET ph thuc vo hai nhm yu t: ccyu t xc nh ch lm vic ca MOSFET v cc yu t pht sinh t cc mchtng tc vi MOSFET.

Nhim v ca chuyn ny l kho st, nghin cu cc tham s xc lp ch

lm vic ca MOSFET c vai tr quyt nh n mc tn tht cng sut trongMOSFET, qua xc lp cc qui trnh ti u ha b tham s ny vi mc ch khngch nhit ca MOSFET, nng cao n nh, tin cy v h gi thnh ca sn

phm trong thit k cc SMPS cho n LED.

6. Phm vi v phng php nghin cu

Phm vi ca ti ny l nghin cu ch nhit ca MOSFET v cc gii phpk thut ti u ha cc tham s hot ng ca MOSFET trong cc SMPS c cngsut di 100W.

Phng php nghin cu thc hin theo qui trnh:

- Kho st v cu trc, nguyn l lm vic, phng php xc nh cctham s hot ng ca MOSFET, t xc nh nhm tham s c nhhng n tn tht cng sut, xc lp ch nhit trong MOSFET.

- Xc lp m hnh nghin cu, phng thc iu chnh v ti u b thams nhm gim thiu tn tht cng sut trong MOSFET.

- Xc lp qui trnh ti u ha b tham s ni trn bng phng phpthc nghim trong qu trnh thit k cc b ngun cho n LED cngsut di 100W.

7. Kho st v MOSFET

Cc SMPS cng sut di 100W thng c thit k theo kiu Flyback hocbuck-boot, c s nguyn l nh sau:

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Hnh 1: S nguyn l ca mt SMPS kiu Flyback

Hnh 2: S nguyn l ca mt SMPS kiu Buck

Trong cc s trn, cc MOSFET c nhim v ng ngt (chuyn mch) cc

dng in trong cc tng PWM v PFC. Ty theo v tr chuyn mch m MOSFETm nhim, hu nh ton b nng lng ca mch s cp hoc th cp s chuyn quaMOSFET. Tn tht ca dng nng lng ny trn MOSFET s chuyn ha thnhnhit nng v c gii phng trn b phn tn nhit ca MOSFET. Cng sut nguncng ln, tn hao cng nhiu v nhit trn MOSFET cng cao.

8.1. Kho st cu trc v nguyn l lm vic ca MOSFET

7.1.1. Cu trc v nguyn l lm vic ca MOSFET

Khng ging nh cc thit b MOSET knh lateral c s dng ph bin trongcng ngh IC m trong cc cc gate, source v drain c t trn cng mt b

mt ca wafer, cc MOSSFET s dng kin trc knh thng ng tng thm khnng xp xp ngun thit b. Trong cu trc knh thng ng, cc cc source v drainc b tr trn hai mt i din ca silicon wafer.

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Hnh 3: Cu trc ca mt MOSFET knh N v k hiu

Hnh 4: (a) Mt ct ngang ng ca MOSFET cng sut v(b) miu t dng n gin cu trc MOSFET

Hnh 4a m t mt ct ngang ca mt MOSFET cng sut. Hnh 4b miu t n

gin mt ct ngang ny. Tip gip p-n gia vng p-base v vng n-drift c kh nngb ph v bi mt in p thun. Di kim loi ca ngun ni trc tip vi vng p-basequa mt lt ct trong vng n+-source to ra mt hiu in th c nh cho vng p-

base trong qu trnh hot ng. Khi in th ti cc cc gate v source nh nhau(VGS=0), vng p-base khng dn in, tc l knh dn in s khng c thit lp(knh cha c iu chnh cho ph hp). Nu t mt in p dng t cc sourcen cc gate s to ra mt dng electron hng v pha cc gate trong vng ch yuca MOSFET. Khi in p gate-source t ti in p ngng, lng electron tch lydi cc gate gy ra mt lp kiu n nghch o; hnh thnh mt knh dn dctheo vng p-body. Cc electron c th chy trc tip trong knh ny. Dng in draindng (hoc dng forward) n drain l dng cc electron t cc source hng ticc drain. Dng drain thun s b ngt khi knh chuyn sang trng thi ng

Hnh 5 th hin cu trc thc t mt ct ngang ca mt MOSFET cng sut knhN vi cc phn t k sinh trn n. Cc phn t ny tham gia vo qu trnh hot ngca MOSFET v c ch gy t tht trong MOSFET.

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Hnh 5: (a) mt ct ngang ca mt MOSFET knh N; v (b) cc phn t k sinhtrong diode

7.1.2. Cc yu t ch yu nh hng ti ch lm vic v tn tht trongMOSFET

7.1.2.1. in tr trng thi m

B phn ch yu ca in tr trng thi m RDS(on) bao gm knh, JFET (lp tchly) vng drift v cc phn t k sinh (phn bc kim loi, dy ni vo bao gi). Tiin p chun trn 150V, in tr vng drift chi phi RDS(on).

Khi MOSFET trong trng thi m (vng triode), knh thit b hot ng gingnh in tr khng i RDS(on) v t l tuyn tnh vi s thay i gia vDS v iD theo

biu thc sau:

(1)

Tn tht cng sut truyn dn (trong trng thi m) tng cng i vi mtMOSFET c dng thun ID v in tr m RDS(on) l:

(2)

Gi tr RDS(on) l ng k v bin i t vi chc milliohms vi cc MOSFET in

p thp n vi ohms i cc MOSFET in p cao. in tr trng thi m l mt

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tham s quan trng trong datasheet, dng xc nh in p ri thun t trn thitb v tn tht cng sut tng cng trn MOSFET.

RDS(on)ph thuc vo dng drain, nhit tip gip Tj v in p nh thngV(BR)DSS.

Hnh 6: Quan h gia in tr trng thi m RDS(on) v dng drain ID

Ti vng in p cao, dng drain t nh hng ti RDS(on). Minh ha trong hnh 6,khi dng in tng gp i, RDS(on) ch tng khong 6%.

Hnh 7: quan h gia RDS(on) v nhit lp tip xc Tj

RDS(on) b nh hng mnh ca nhit , hnh 7 m t mi quan h gia RDS(on) vnhit ti lp tip xc Tj. Khi nhit tng t 25oC n 125oC, RDS(on) tng gp i.H s nhit ca RDS(on) l dc ca ng cong trn hnh 3 v lun dng trongch c ti. H s nhit dng ln nh hng xu ti tn tht truyn dn (I2*R)

khi nhit tng.

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Hnh 8: quan h RDS(on) v V(BR)DSS

RDS(on) cng tng mnh khi tng in p chun V(BR)DSS nh m t hnh 8, trong RDS(on) t l vi bnh phng ca V(BR)DSS. Mi quan h phi tuyn gia RDS(on) vV(BR)DSS l l do hp dn nghin cu cch gim tn tt truyn dn ca transistor.

7.1.2.2. JFET

Trong cu trc ca MOSFET, hnh thnh mt JFET y nh th hin trong

hnh 1. JFET ny c nh hng ng k ln RDS(on) v l mt phn ca hot ng bnhthng ca MOSFET.

7.1.2.3. Diode ni ti (Internal Body Diode hoc Intrinsic Body Diode)

MOSFET cng sut hin i c mt diode ni ti c gi l body diode ni giasource v drain nh m t trong hnh 9a. Diode ny cung cp mt phn hi trc tipi vi dng drain, b xung chuyn mch hai chiu. Mc d body diode caMOSFET c dng ph hp v tc chuyn mch nhanh, trong mt vi ng dngca in t cng sut c yu cu s dng thm mt ultra-fast diode, l mt diode

phc hi nhanh bn ngoi dng song song ngc, sau loi b body diode bng mtdiode phc hi chm nh hnh 9b.

Hnh 9: (a) Diode ni ti trong; v (b) phng thc

b xung mt diode phc hi nhanh7.1.2.4. Internal Capacitors

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Tham s quan trong khc gy nh hng ti hnh vi chuyn mch l cc indung k sinh gia ba cc ca thit b, c th l gate-source (Cgs), gate-drain (Cgd) vdrain source (Cds) m t trong hnh 6.9a. Gi tr ca cc in dung ny l phi tuynv l hm ca cu trc thit b, hnh dng v in p nh thin. Trong qu trnh m,cc t Cgd v Cgs cn phi c np qua gate, do , vic thit k mch iu khin

cng gate cn phi c xem xt s bin i trong cc t ny. S bin i ln nhtgy ra trong tu Cgd (gate-to drain) l s bin thin in p drain-to-gate. in dungk sinh trong MOSFET c cho trong mi quan h gia cc tham s trong datasheetca thit b Ciss, Coss, v Crss nh sau:

y, Crss l in dung truyn ngc tn hiu nh, Ciss l in dung vo tn hiunh khi cc drain v source ngn mch; v Coss l in dung ra tn hiu nh khi cccc gate v source ngn mch. Cc in dung Cgs, Cgd v Cds l phi tuyn v l hmca in p nh thin. S bin thin ca Coss v Ciss l quan trong v in p drain-to-source v in p gate-to-source ln lt qua im 0. Mc tiu ca mch iukhin l ln lt np v phng cc t in k sinh gate-to-source v gate-to-drain khim v ng mch.

Hnh 10: (a) M t cc in dung k sinh trong MOSFET; v(b) miu t v tr vt l ca cc in dung k sinh

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8.2. Kho st c ch sinh nhit v phng php tnh tn tht trong MOSFET

7.2.1. Tn tht ca MOSFET v Diode

Tn tht cng sut (Pl) trong bt k mt linh kin no hot ng trong ch chuyn mch c th phn thnh ba nhm:

- Tn tht truyn dn (Pc)- Tn tht chuyn mch (Psw)- Blocking (leakage) losses (Pb), thng c b qua

Do :

(3)

7.2.2. Tn tht truyn dn

Tn tht truyn dn trong MOSFET cng sut c tnh bng cch s dng mtMOSFET tng ng vi in tr drain-source trng thi m (RDSon):

(4)

Trong , uDS v iD ln lt l in p drain-source v dng drain. Thng thngRDSon c th c xc nh trong biu ti datasheet nh hnh 1, khi i D l dngqua MOFET trng thi m ti cc ng dng tng ng.

Hnh 11: S ph thuc ca in tr drain-source vo dng drain (ti Tj=25oC)

Do , gi tr tc thi ca tn tht truyn dn ca MOSFET l:

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(5)

Tch phn tn tht cng sut tc thi trn chu trnh chuyn mch cho gi tr trungbnh tn tht truyn dn trn MOSFET

(6)

Trong , IDrms l gi tr hiu dng ca dng drain qua MOSFET trong trng thim.

Tn tht truyn dn ca anti-parallel diode c th c tnh bng cch s dngmt diode tng ng mt kt ni ni tip ca mt ngun in p mt chiu DC cin p (uD0) tng ng vi in p ca diode trong thi ng v in tr RD ca

diode trng thi m, uD l in p ri trn diode khi dng iF chy qua:

(7)

Cc tham s ny c th xc nh t biu trong datasheet ca MOSFET biu thtrong hnh 2. c cc tham s bin i khi a vo tnh ton v do c mt tnhton ph hp, gi tr uD0 c c t biu phi t l vi (uDmax/uDtyp). Gi tr ktxut c th c ly t datasheet, trong tnh ton thit k, gi tr ny cho php daong t 10% n 20%.

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.Hnh 12 : S ph thuc ca in tr diode vo dng diode

Tn tht truyn dn tc thi ca diode l:

(8)

Nu dng in diode trung bnh l Ifav v dng in diode hiu dng l Ifrms, tntht truyn dn trong chu k chuyn mch (Tsw=1/fsw) l:

(9)

Chn nhit v s bin thin a vo tnh ton

Qui trnh xc nh RDSon biu th trn hnh 1, v tham kho thm gi tr RDSonthng dng. Qui trnh ny p ng c hu ht cc ng dng, gi tr RDSon c th tnhton c bng cch tnh nhit v s bin i nhit qua biu thc sau:

(10)

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y, TJ l nhit tip xc v RDSonMAX(25oC) l gi tr cc i ca RDSon ti25oC, m c th xc nh t bng tng hp tham s trong datasheet ca sn phmtrong hnh 3. H s nhit c th tnh theo cch nh sau: Hai b gi tr (TJ1, RDSon1)v (TJ2, RDSon2) c th xc nh t datasheet nh hnh 4. Cc gi tr ny c dngtrong phng trnh sau xc nh

Hnh 13: Xc nh gi tr RDSonMAX(25C) t data-sheet

Hnh 14: Xc nh TJ/RDSon t the data-sheet

7.2.3. Tn tht chuyn mch

Mch in kim tra tn tht chuyn mch ca MOSFET c m t trong hnh5. l mt single-quadrant chopper cp ngun cho mt cun cm ng vai tr ti.MOSFET c iu khin bi mt mch iu khin, cung cp in p UDr ti u raca n. Diode trong MOSFET ng vai tr nh mt free-wheeling diode, do tronghu ht cc ng dng, b converter in t cng sut cha mt hoc nhiu MOSFET

nn tng ca cc cu na chu k.. Nu s dng mt freewheeling diode bn ngoi,su tnh ton vn hiu lc, trng hp ny, cc tham s ca diode xc nh tdatasheet ca diode.

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Hnh 15: mch kim tra tn tht chuyn mch ca MOSFET

tnh ton thit k cn bng tn tht cng sut, s xp x tuyn tnh ca qutrnh chuyn mch MOSFET l chp nhn c xem xt tnh ton cc trng hpxu nht. Qu trnh chuyn mch l tng ha ca mt MOSFET c trnh bytrong hnh 6. Phn (A) biu din in p (uGS) v dng (iG) gate. Phn (B) biu dinip p (uDS) v dng drain (iD) khng tnh n s phc hi ngc ca free-wheelingdiode. Phn C biu din nh tnh ca tn tht cng sut mt cch tng qut v phn D

biu th hiu qu ca s phc hi ngc trn tn tht chuyn mch.

7.2.3.1. Qu m chuyn mch

- Mch iu khin thay i trng thi t 0V n UDr, in p ti cng gate

nng ln n in p ngng (UGS(th)) vi thi gian khng i c xc nhin tr gate v in dung u vo tng ng ca MOSFET(Ciss=CGD+CGS). Cho n khi in p gate t ti in p ngng U GS(th),u ra khng thay i

- Sau khi t c in p ngng UGS(th), dong drain tng ln t ti dngin ti. Xc nh thi gian tng dng (tri) gia 0 v IDon (c xc nhtrong tng ng dng) trong trng hp xu nht c th xc nh trongdatasheet ca MOSFET ti hnh 17. Trong qu trnh dng in tng, free-wheel diode vn dn in do in p drain-source l UDD.

- diode chuyn sang trng thi ng, tt c cc minority carriers stored in

it phi c loi b (xem hnh 16D). Dng in phc hi ngc cMOSFET tiu th v gy ra mt tn tht cng sut b xung. Vic nh gitrng hp xu nht ca reverse-recovery charge (Qrr) v khong thi gian

phc hi ngc (trr), m c s dng trong tnh ton tn tht cng sut, cth xc nh t datasheet ca MOSFET (hnh 18).

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Hnh 16: Qu chuyn mch trn MOSFET cng sut

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Figure 17 Reading the current rise- (red) and fall-time (blue) from the data-sheet

Figure 18 Reading the reverse recovery time (red) and charge (blue) from the data-sheet

Sau khi diode chuyn sang ng, in p drain-source gim t uDS=UDD n gi tr trng thi m uDS=RDSon*Ion. Hiu ng Miller xy ra v in p gate-source b kp tigi tr uGS=U(plateau) (xem hnh 19). dc ca in p drain-source b quyt nh

bi dng gate qua t in gate-drain (CGD=Crss). tnh thi gian gim in p (t fu)vi mt chnh xc chp nhn c, khng tuyn tnh ca in dung gate-draincn c a vo trong tnh ton. Thng thng s ph thuc ca in dung gate-drain vo in p drain-source c biu th trong hnh 20. Do kh khn trong victnh n phi tuyn trong tnh ton thit k, nn c th s dng hai im xp xtrong tnh ton thit k. Phng php ny cho rng nu in p drain-source trong

phm vi uDS.[UDD/2,UDD], khi in dung gate-drain nhn gi tr CGD1=CGD(UDD).Mt khc, nu in p drain-source trong phm v uDS.[0V,UDD/2], khi in dunggate-drain nhn gi tr CGD2= CGD(RDSonIon). Cch xc nh in dung biu th tronghnh 20 bng cch hai im xp x c a vo tnh ton, in p drain-source trongkhong thi gian gim c biu th bi ng t on trn hnh 16B. Phng phpny ch s dng xc nh thi gian gim ca in p (cng nh xc nh thi giantng khi chuyn mch ng). V in p drain-source c gi thit c dng tuyntnh (ng lin hnh 16B), iu ny gip trnh phn tch r rng trng hp xunht tnh tn tht chuyn mch.

Dng in gate trong thi gian tfu c tnh theo cng thc:

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(11)

Thi gian gim in p c tnh l im gia ca thi gian gim tnh theo dng

gate v t in CGD1 v CGD2.

(12)

Trong :

(13)

Figure 19 Reading the plateau voltage from the data-sheet

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Figure 20 Two-point representation of the gate-drain capacitance7.2.3.2. Qu ng chuyn mch

Qu trnh ng chuyn mch tng t vi qu trnh m chuyn mch caMOSFET theo mt trnh t ngc li, nhng c hai im khc quan trng l:

- Khng din ra phc hi ngc- Dng gate v thi gian tng c th tng nhanh do:

(14)

(15)

7.2.3.3. Nng lng chuyn mch v tn tht

Nh trnh by trong phn trc, tn tht nng lng chuyn mch m trongMOSFET (EonM) c tnh ton l tng ca nng lng chuyn mch m khng tnh

n qu trnh phc hi ngc (E onMi) v nng lng chuyn mch m gy ra bi free-wheeling diode (EonMrr).

(16)

nh dng phc hi ngc c xc nh theo cng thc:

(17)

Nng lng m trong diode ch yu l nng lng phc hi ngc(EonD):

(18)

Trong , UDrr l in p dc theo diode trong thi gian phc hi ngc. i vitrng hp xu nht vic tnh ton in p ny c th xy x vi in p cp(UDrr=UDD). Tn tht nng lng ng chuyn chuyn mch trong MOSFET c th

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c tnh ton cng theo cch . Tn tht ng chuyn mch trong diode thngc b qua (EoffD0). Do :

(19)

Tn tht chuyn mch trong MOSFET v diode l tch ca nng lng chuynmch v tn s chuyn mch (fsw):

(20)

7.2.3.4. Loss Balance

Tn tht cng sut trong MOSFET v free-whelling diode c th c biu thnh tng ca tn tht truyn dn v tn tht chuyn mch:

(21)

8.3. Cc tham s trong cc mch ng dng lin quan n ch hot ng ca

MOSFET trong phm vi chuyn Mc di y xem xt c th cc tham s trong mch converter cn xc nh

trong tnh nhit ca MOSFET.

7.3.1 Step-down (Buck) Converter

Hnh 21 v 22 trnh by topology v dng sng thng dng trong mch step-down(buck) converter.

Figure 21 Step-down converter topology

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Figure 22 Step-down converter typical signals

Cc tham s u vo dng trong tnh ton thit k: in p u vo (Uin), in pu ra (Uo), cng sut u ra (Po), gi tr t cm (L), tn s chuyn mch (fsw).

Dng in u ra:

(22)

Chu trnh duty trong ch dn lin tc:

(23)

gn dng u ra:

(24)

Cc tham s cn thit tnh tn tht c th xc nh ph hp vi cc gi tr tnhton phn trn:

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(25)

7.3.2 Step-up (Boost) Converter

Hnh 23 v 24 trnh by topology v dng sng thng dng trong mch step-upconverter.

Figure 23 Step-up converter topology

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Figure 24 Step-up converter typical signals

Cc tham s u vo dng trong tnh ton thit k: in p u vo (Uin), in pu ra (Uo), cng sut u ra (Po), gi tr t cm (L), tn s chuyn mch (fsw).

Dng in u ra:

(26)

Chu trnh duty trong ch dn lin tc:

(27)

gn dng u ra:

(28)

Cc tham s cn thit tnh tn tht c th xc nh ph hp vi cc gi tr tnhton phn trn

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(29)

8. Ni dung nghin cu

8.1. M hnh kho nghim

Khng lm mt i tnh tng qut ca chuyn , m hnh tin hnh cc nghincu c xut l b ngun chuyn mch kiu boot-buck cho cc b n LED chiusng cng sut n 100W.

B ngun chuyn mch kho nghim c thit k trn nn tng IC L6562 caHng ST Microelectronics. B ngun c thit k gm hai tng, tng boot vi mchPFC kiu tch cc, c vai tr cp ngun in 1 chiu in p 400 V cho tng buck.Tng buck vi mch PWM l trung tm, m nhim vic cung cp ngun cho ti. HaiMOFET c s dng trong b ngun l STP8NM50FP (cho tng boot) v

STP9NM50N (cho tng buck) (hnh 25).

Figure 25. block schematic

Trong hai MOSFET trn, MOSFET STP9NM50N phi lm vic trong ch khc nghit hn, c bit khi b ngun phi cung cp cho ti mt dng in ln vicng sut ln. V vy cc nghin cu s thc hin MOSFET ny.

8.2. Nguyn l lm vic ca b ngun v cc yu t lin quan n MOSFET

Nguyn l c bn ca thit k b ngun chuyn mch s dng IC iu khin

L6562A c th hin trn hnh 1 v hnh 2. Hnh 1 trnh by trng thi ca tng buckkhi MOSFET Q1 trng thi m. Khi , c dng in i t ngun (in p 1 chiu

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u vo Vin) qua ti (LEDs), cun cm (L), MOSFET cng sut (Q1) v in trsensing (in tr nhy dng - Rs) (ng ). T in C4 c np qua diode D2 vin tr R5, do , MOSFET Q1 c m v in p t ln cc gate ca MOSFETc duy tr khong 10V. Trong thi gian m ton, dng ti (dng drain) tng ln vdng li cng sm cng tt khi in p ri trn in tr nhy dng Rs t ti ngng

ni b trn chn CS ca IC L6562A. Dng in sense ca L6562A b kp ti in p1.08V. Hnh 2 m t s bin thin ca cc tham s khi MOSFET chuyn sang trngthi ng. Cun cm L s duy tr vic cung cp dng in cho ti v mch in ckhp kn qua diode D1. Dng in ti gim dn xung gi tr cc tiu, gi tr ny cthit lp bi mng thi gian ng khng i (Thi gian t OFF lun l mt hng s) nht in C4 phng in qua in tr R4. in p trn t C4 c ni vi chn ZDC(zero curent detector) ca L6562A. T in C4 phi phng in in p ca ngim xung ngng 0,7V cng sm cng tt (ngng ca ZCD), L6562A chuynmch MOSFET v dng in ti li tng tr li. Qu trnh ny c lp li tng chuk mt nh biu th trong hnh 26 v hnh 27.

Figure 26. Modified buck converter - tONtime

Figure 27. Modified buck converter - tOFFtime

8.2.1. Mch tch hp iu khin L6562

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Mch tch hp iu khin L6562 dng iu khin cc MOSFET trong bngun chuyn mch. L6562 dng iu khin MOSFET hot ng mt trong haich :

- Ch thi gian m c nh (dng trong mch iu khin PFC);

- Ch thi gian ng c nh (trong mch converter).Mch L6562 c s khi nh hnh 18.

Figure 18. Block Diagram

L6562 c cc khi chc nng sau:

8.2.1.1. Khi ngun (hnh 19)

Bao gm b so snh in p thp (undervoltage) vi tr v dng cp rt nh

Figure 19: Supply Block Diagram

8.2.1.2. Khi pht hin qu p v khuch i li (hnh 20)

u vo b khuch i li qua t s ca hai in tr R1 v R2 bn ngoi c nimch ra, cho php phn hi iu chnh s tng ca in p mt chiu u ra. u

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ra ca b khuch i li c ni vi t b Ccomp lc the twice rectified mainsfrequency. Tn hiu ly t cc chn ny cng dng bo v qu p. Do t b chm

phn ng khuch i li, trong khi c b xung mt b d bo v qu p phn ngnhanh.

Figure 20: Error Amplifier and Overvoltage Detector Block

Trong iu kin trng thi xc lp, dng in qua R1 bng dng qua R2 do t bkhng cho php dng mt chiu qua:

(30)

Khi in p u ra tng, dng in qua R1 tng t ngt lm in p ri trn R1

tng mt lng l V, do dng in trn R2 b c nh bi in p tham chiu l2,5V, lng in tng thm s i qua t b vo IC L6569A v c so snh vi dngin tham chiu 40A. Nu gii hn ny b vt qu b bo v qu p s pht hin.Khi s kin ny vt qu mt khong thi gian n nh, tc l s qu p vn tip tcdin ra, u ra ca b khuch i li s gim xung v tr thp, iu kin qu p sc xc nhn, b bo v qu p s sng iu khin v MOSFET bn ngoi s ngmch cho n khi cc iu kin qu p b loi tr. Trong thi gian bo v qu p, ttc cc khi s c dng hot ng (ngoi tr b kp ZDC), cng sut tiu th gim.B bo v qu p gii hn mc tng in p V qua biu thc:

(31)

8.2.1.3. Khi trigger v nhn din dng Zero (hnh 21)

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Figure 21: Zero Current Detection and Triggering Block

Khi xc nhn dng zero chuyn mch m cho MOSFET bn ngoi khi in pt trn cun cm (boost inductor) qua im khng (sau khi dng in qua boostdiode tng vt ngng).

c im ny cho php gim nng lng in dung drain tng ng s ctiu tn trn MOSFET v in p drain nh hng thp trong trng thi m (Virmsthay v Vo). khi ng c mch m khng cn phn h tr bn ngoi, mt xung

bn trong IC c to ra vi tc lp l l 45 70 s, buc b iu khin pht ramt xung hp (200-300ns) n cc gate ca MOSFET, to ra tn hiu cho ZDC. Mtkhc, h thng lm vic ng, tn s chuyn mch cn cao hn 23 kHz.

8.4.1.4. Khi nhn (Multiplier Block - hnh 22)

Khi nhn pht tn hiu lp tr cho b so snh dng.

Figure 22: Multiplier Block Diagram

8.4.1.5. Khi so snh dng v kha an ton cho PWM (hnh 23)

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Figure 23: Current Comparator and PWM Latch

B so snh dng cm nhn in p ri trn in tr nhy dng Rs, so snh n vi

tn hiu lp trnh pht ra t khi nhn, to ra s iu bin chuyn mch.8.4.1.6. Khi iu khin (hnh 24)

Figure 24: Driver

Mt b m totem pole vi 400 mA, ngun v kh nng nh cp pht choMOSFET bn ngoi chuyn mch ti tn s cao.

8.2.2. Mng thi gian ng c nh (Fixed off-time network)

Mng thi gian ng c nh (FOT) l mch c nh thi gian ng caMOSFET khi hot ng, trong m hnh th nghim l mng RC, c tnh ton tmi quan h gia chu trnh ti, tn s chuyn mch v thi gian ng:

(32)

Trong :

- f = l tn s chuyn mch trong switching frequency in CCM (Hz)

- T = period in CCM (s)- D = duty cycle (-)

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Thi gian ng toffc tnh theo biu thc:

(34)

Trong mch buck converter s dng mng FOT, thi gian ng c thit lp bit R4 v C4 (hnh 16). Trong thi gian m, in p cc gate ca MOSFET trng thicao, diode D2 m v in p ti chn ZDC b kp ti V ZCD_CLAMP = 5.7 V. Trong thigian ng, in p cc gate ca MOSFET trng thi thp, diode D2 ng v in pZDC gim theo qui lut s m:

(35)

in p ti chn ZDC gim cho n khi t c gii hn kch thch ni cho phpchuyn mch sang trng thi m. in p xung i vi L6562A l 0,7V. Thi giancn thit in p ZDC t VZDC-CLAMP n VZDC-TRIGGER c xc nh trong khongthi gian ng tOFF:

(36)

Trong :

- VZCD l in p trn chn ZDC ca L6562A (V)

- VZCD_CLAMP l in p kp trn chn ZCD ca L6562A (V)

- VZCD_TRIGGER l in p trn chn ZCD ca L6562A (V)

T C4 v in tr R4 c c th c tnh v chn theo cc biu thc sau:

(37)

in tr R5 (hnh 16) c thit k gii hn dng in np cho t C4 trong thigian m, cn nm trong phm vi sau:

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(38)

Trong :

- VF l in p thun trn diode D2 (V) (thng thng 0,7 V)

- VZCD_CLAMP l in p kp trn chn ZCD ca L6562A (V) (5.7 V)

- VGD_MAX l in p iu khin cng getae cc i trng thi cao (V) (15V)

- VGD_MIN = l in p iu khin cng gate cc tiu ti cc trng thi cao(V) (9.8 V)

- IZCD_MAX l kh nng cp cc i i vi chn ZCD (A) (0.01 A)Nu thi gian tON l qu ngn (ti hoc in p thp), t C4 s khng c np

nhanh qua R5. Trng hp ny c th ni thm t C3 song song vi R5. Gi tr cci ca t C3 c th c tnh theo biu thc sau:

(39)

8.2.3. MOSFET cng sut

MOSFET cng sut c chn theo in p xung cc i, dng MOSFET nhcc i, tn tht cng sut tng cng, nhit hot ng cho php cc i v khnng iu khin ca L6562A.

in p xung cc i trn MOSFET (drai-source) vi mch buck trong m hnhl in p u vo. MOSFET cng sut c la chn vi mt in p d tr trnin p ny, v d, nu in p u vo cc i l 400V, khi in p drain-sourcecc i s l 450V hoc cao hn.

Dng MOSFET nh c chn tnh kch c cun cm v cng c chn vidng d tr.

8.2.3.1. Tn tht truyn dn

Tn tht cng sut tng cng trn MOSFET cng sut cn c tnh ton do tmquan trng ca vic thit k phn t tn nhit ph hp trnh xung nhit trnMOSFET. V c bn, tn tht tng cng trn MOSFET xy ra qua tn tht truyn dn(ph thuc vo in tr RDS(ON), tn tht chuyn mch v tn tht np gate (do phinp cc t in gate sau khi cc t ny phng ht xung t). Tn tht np cho cnggate l rt nh so vi tn tht dn v tn tht chuyn mch, nn thng c b qua.V th, tn tht tng cng trn MOSFET c tnh theo biu thc:

(40)

Trong :

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- PTOT l tn tht tng cng trn MOSFET cng sut (W)

- PCON l tn tht truyn dn trn MOSFET cng sut (W)

- PSW l tn tht chuyn mch trn MOSFET cng sut (W)

Tn tht truyn dn trong MOSFET cng sut c miu t bi dng in lin

tc qua MOSFET tong trng thi m. Do , tn tht truyn dn ph thuc vo intr drain-source tnh RDS(ON). tnh ng tn tht truyn dn, cn phi tnh gi trhiu dng cu dng drain. Hnh 25 biu th dng dng drain dng tnh ton.

Figure 25. Sawtooth signal

Gi tr hiu dng ca dng drain c tnh theo biu thc sau (Lu rng gi trdng trung bnh IAVG c tnh theo gi tr trung bnh ca cc phn rng ca

(IMAX+IMIN/2))

(41)

Trong :

- IRMS l gi tr hiu dng ca dng drain (A)

- IPP l dng peak-to-peak (A) (khc vi IMAX v IMIN)

Gi tr thc ca dng sng dng drain trong hnh 26 nh quan st c hon tonging dng sng trong hnh 25, ngoi tr l khng c dng trong khng thi gianMOSFET ng (IO=0). Trn hp ny, gi tr hiu dng cu dng drain c tnhtheo bieur thc:

(42)

Trong :- IAVR_ON l dng in trung bnh trong khong thi gian m tON (A).

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V vy, tn tht truyn dn l:

(43)

Trong :- RDS(ON) l in tr tnh drain-source ca MOSFET ().

Figure 26. Real drain MOSFET current

8.2.3.1. Tn tht chuyn mch

Tn tht chuyn mch ph thuc vo thi gian chuyn mch, dng drain, in p

drai-source v tn s chuyn mch. Thi gian chuyn mch, thi gian tng, thi giangim l hm ca s np in cho cc in dung k sinh ti cng gate, in tr bntrong ca b iu khin, in p ngng VGS(TH) v in p cc tiu ti cng gate cho

php dng drain-source i qua.

Hnh 27 biu th s bin thin thc t ca cc i lng trong qu trnh chuynmch.

Figure 27. Power MOSFET turn ON and OFF measurement

Do tnh cht khng tuyn tnh ca cc qu trnh ny, vic tnh ton chnh xc tntht chuyn mch l rt phc tp. n gin cho qu trnh tnh ton m vn m bo chnh xc kt qu tnh chnh mc chp nhn c, tn tht chuyn mch ctnh theo cng thc sau:

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(44)

Trong

- tOFF_SW l thi gian ng chuyn mch (s) (thng l vi chc ns).

Cng sut tng cng (PTOT) mt mt trn MOSFET v tn nhit c tnh tonn gin nh sau:

(45)

Trong :

- TJMAX l nhit cc i ca lp tip gip (C)

- TA l nhit mi trng (C)

- RthJC l in tr nhit tip gia gip-v (C/W)

- RthCH - in tr nhit gia v-tn nhit (C/W)

- RthHA l in tr nhit gia tn nhit-mi trng (C/W)

Nu bit tn nhit v in tr nhit ca n, c th tnh c in tr tnh cci drain-source v t chn MOSFET:

(46)

8.3. Ni dung nghin cu

8.3.1. nh hng nghin cu

Bn cht ca khng ch nhit lm vic ca MOSFET l gim tn tht truyndn v tn tht chuyn mch ca MOSFET trong qu trnh hot ng di ngngcho php. Nhng ni dung kho st ti mc 7 v mc 8.2 cho thy nhm tham s lin

quan ch yu n tn tht trong MOSFET (hay c ch sinh nhit ca MOSFET) trongqu trnh hot ng bao gm: tn s chuyn mch (fsw), dng drain (I D), in trdrain-source trong thi gian m RDS(ON),thi gian tng v h trong chuyn mch (t f vtr). V vy, vic la chn b tham s ti u ca MOSFET trong qu trnh hot ngtheo hng gim thiu tn tht v khng ch nhit hot ng ca MOSFET cthc hin theo hng xc lp cc gi tr ti u ca cc tham s ny.

Vic xc nh gi tr ti u ca tham s c thc hin theo phng php thcnghim qua cc bc:

- Xc nh mc tiu thit k sn phm.

- Tnh ton thit k sn phm v la chn linh kin theo cc kt qu tnhton l thuyt

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- Ti u ha cc b tham s bng phng php thc nghim theo qui trnhxc nh nhm t mc tiu thit k t ra, thc hin iu chnh v bxung danh mc linh kin.

8.3.1.1. Ti u ha tn s chuyn mch

nh hng ca tn s chuyn mch ti tn tht cng sut c m t trong ccbiu thc (20), (44). Mi quan h ch ra rng, tn s chuyn mch nh hng chyu ti tn tht chuyn mch theo xu hng tn s chuyn mch cng tng, tn thtchuyn mch cng tng.

Tuy nhin, mc tiu trong in t cng sut l s dng thit b chuyn mch cngsut hot ng tn s cng cao cng tt v khi , kch c ca cc bin p, cuncm, v t lc s gim. Do , s dng cc MOSFET c tn s chuyn mch cao l xuhng thit k b ngun chuyn mch hin i.

Nh vy, nh hng ti u ha tn s chuyn mch phi dung ha c hai xuhng ny, tc l xc lp c tn s chuyn mch cao nht m vn m bo c

tn tht chuyn mch mc chp nhn c v nhit lm vic ca MOSFET ckhng ch mc cho php.

8.3.1.2. Gim thiu tn tht truyn dn qua ti u ha RDS(ON) v dng drain

Tn tht truyn dn trong MOSFET trng thi m bng tch ca bnh phngdng drain v RDS(ON) (biu thc 5, 6 mc 7), do tn tht ny cng t nu dng drainv RDS(ON) cng nh.

Trong cc b ngun chuyn mch, ln ca dng drain ph thuc vo ti. do, khng th gim dng drain xung mt ngng no . Mt khc, dng drain,RDS(ON), nhit lp tip gip Tj v loi MOSFET c la chn c lin quan cht chvi nhau (nh m t mc 7.1) nn vic gim thiu tn tht truyn dn phi t ctrn c s ti u ha b tham s ny.

Vic nghin cu nhm xc lp qui trnh ti u b tham s ni trn bng thcnghim qua trnh t cc bc:

- La chn MOSFET trn c s tnh ton thit k, nh gi mc mc tntht thng qua nhit lm vic ca MOSFET.

- Thc hin gim Tj thng qua vic tng phn t tn nhit, gim tn thtcng sut trn anti-parallent diode hoc b xung MOSFET song song,hng ti xc lp mt b thng s ti u.

8.3.1.3. Ti u ha thi gian tng trv thi gim tf

Thi gian tng tr v thi gian gim tf ph thuc vo thi gian phng v np cc tk sinh CDG v CGS (mc 7.2). B tham s ny ph thuc vo dng cc gate. Vi mtloi IC iu khin c la chn, cn ti u mch cc gate t c gi tri t r v tftt nht nhm gim thiu tn tht chuyn mch.

8.3.2. Thit k b ngun mu

Nh trnh by mc 8.1, b ngun chuyn mch mu dng cho nghin cutrong chuyn ny c thit k theo khuyn ngh ca ST Microelectronics tiSTEVAL-ILL013V1 (UM0670 User manual 80 W offline LED driver with PFC).

S mch ca tng boost v buck c trnh by trong hnh 28 v 29.

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Figure 28. High PF boost converter design concept

Figure 29. Modified buck converter design concept

Trong s :

- Cp in tr R203 v t in C204 dng xc lp tn s chuyn mch.

- in tr R201 hn ch dng in cc gate.

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- MOSFET Q201 c iu khin bi IC 6562A iu bin dng drain.

8.3.3. Danh mc vt t

Reference Q'ty Part 100W Note

F1 1 7A/250V FuseBR1 4 1N4007 Diode bridge

C104 1 100nF/630VAC ceramic capacitor

C105 1 10nF/63V ceramic capacitor

C106, C202 2 100nF/63V ceramic capacitor

C107 1 10uF/35V Electrolytic capacitor

C108,C109 2 12nF/63V ceramic capacitor


C111 1 2200nF/25Vx7R ceramic capacitor

C112 1 150nF/50V ceramic capacitor


D101 1 18V/0.5W Zener diode

D102,D104,D201 3 1N4148

D103 D203 2 STTH1L06

U101, U201 2 L6562N PFC controller

R103, R104 2 1 M

R105 1 6,8 k

R106, R107 2 270 kR108, R109 2 47

R110, R116, R208 3 47 k

R113, R114 2 1 / 1%

R115 1 33

R117 1 22 k

R118, R119 2 1 M / 1%Axial resistor 0.6 W /1%

R120 1 15 k / 1%

R121 1 82 k / 1%

R123, R124, R125 3 330 k For dimming

R126, R127 2 20 k For dimming

R128 1 43 k For dimming

T101 1

EI30/21/10.7 gap3,PC40, Primary: 105turns 0.5mmSecondary: 9 turns

0.2mm

Transformer

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Q101 1 STP8NM50 Power MOSFET

Q102 1 BUX87Bipolar transistor (fordimming)

D204 1 1N4148 For dimming

Heat sink 4 Heat sink forMOSFETs

R202, R207 2 1k

R201 1 5 Axial resistor

R204 1 1 / 1 W/1% Axial resistor

R205 1 1 / 1 W/1% Axial resistor

R203 1 5,6 K Axial resistor

C201 1 22 F / 35 V Electrolytic cap

C203 1 220pF / 63 V ceramic capacitor

C204 1 4,7 nF / 63 V ceramic capacitor C208 1 47 F / 450 V Electrolytic capacitor

C208.1 1 22 F / 450 V Electrolytic capacitor

L 1 4,7 H

D202 1 STPSC806D Silicon carbide diode

D201.1,D201.2 2 1N4148

R201.1,R201.2 2 4,7 Axial resistor

R201, R201.3 2 10 Axial resistor

AC in, DC out 2 Socket Output socketQ201 2 STF9NM50N Power MOSFET

L201 1800uH-55 vong-EI33/21/10.7-G4

8.3.4. Kt qu thc nghim v gii php xut

8.3.4.1.Nghin cu nh hng ca tn s chuyn mch ti nhit lm vic caMOSFET

(a) M hnh th nghim: b ngun chuyn mch c thit k cho n LED ccng sut 100W nh m t trong mc 8.3.2 v 8.3.3. Cc tham s in ca

b ngun nh sau:

o Tn s chuyn mch: 60 kHz

o Dng drain: 3A

(b) Qui trnh th nghim: Xc lp mi quan h gia tn s chuyn mch vnhit lm vic ca MOSFET (nhit trn tn nhit ca MOSFET) theo

phng thc iu chnh cp in tr R203 v t C203 gim dn tn schuyn mch t 60 kHz xung 25 kHz (km theo vic iu chnh cc phn

t trong mch cng sut nh cun cm L, diode D202, t in C208) .

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Lp th mi quan h f(tM, fsw) kho st s bin thin ca nhit MOSFET tM theo tn s chuyn mch fsw.

Xc nh tn s chuyn mch ti u ca b ngun thit k.

(c) Kt qu thc nghim

Cc kt qu thc nghim c m t theo trn biu sau

nh hng ca tn s chuyn mch nnhit ca MOSFET

64 65 6876

98

0

20

40

60

80

100

120

Tn s chuyn mch (kHz)

NhitMOSFET(oC)

Series2 64 65 68 76 98

25 33 41 50 60

(d) Nhn xt kt qu th nghim

T nhng kt qu thc nghim, c th rt ra cc kt lun sau:

- Tn s chuyn mch c nh hng ln ti tn tht trn MOSFET, biuhin qua nhit lm vic ti ch xc lp ca MOSFET. S nhhng ny l phi tuyn. gii tn s nh, mc nh hng t thayi.

- Qui trnh thit lp tn s chuyn mch ti u c thc hin theo chutrnh gim dn thng qua vic gim st nhit lm vic ca MOSFET ch xc lp. Thi gian cn thit cn bng nhit khi MOSFETlm vic ch xc lp ti thiu l 30 pht.

- Gi tr tn s chuyn mch ti u l gi tr ngng m ti vic gimtn s chuyn mch nh hng t ti nhit ca MOSFET v khng

lm tng kch thc ca cc linh kin trong mch ti.8.3.4.2.Nghin cu nh hng ca dng drain v in tr RDS(ON) ti nhit

lm vic ca MOSFET

(a) M hnh th nghim: ging nh mc 8.4.2.1, sau khi c ti u hatn s chuyn mch.

(b) Qui trnh th nghim: sau khi ti u tn s chuyn mch, nu nhit caMOSFET trng thi xc lp vn ngng cao, cn tip tc gim nhit ca MOSFET theo cc hng:

- B xung free-whell diode bn ngoi cho MOSFET nh khuyn ngh

trong mc 7.1.2.3

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- Thc hin tng s lng MOSFET theo phng thc mc song song.Phng thc ny cho php gim dng drain trn MOSFET, nhng lu trong trng hp ny, tn tht chuyn mch tng.

(c) Kt qu thc nghim: thc hin thay th mch mt MOSFETSTF9NM50N bng hai MOSFET STF9NM50N ni song song, nhit ln vic ca MOSFET gim t 65oC xung cn 55oC ti im nng nhttrn tn nhit ca cp MOSFET.

(d) Nhn xt kt qu th nghim: gii php gim dng drain bng phngthc tng lng MOSFET l cn thit nu nhit hot ng trnMOSFET vn mc cao, c th lm gim tin cy v tui th ca sn

phm.

8.3.4.3.Nghin cu nh hng ca dng cc gate ti nhit lm vic caMOSFET hng ti ti u trv tf

(a) M hnh th nghim: ging nh mc 8.4.2.1. Dng in cc gate c quinh bi IC L6562A v in tr R201. Theo thit k, in tr R201 c gitr l 33. Gi tr ny qui nh dng in gate khi mch chuyn trng thit ng sang m hoc ngc li. Dng gate ln cho php cc t Cdg vCgs nhanh chng c np y hoc phng ht, do in p cc gatenhanh chng t ngng m hoc ngng ng, tng ng l thi gian t rv tf gim, v vy tn tht chuyn mch gim.

(b) Qui trnh th nghim: xy dng mi qua h gia in tr R201 vi nhit MOSFET.

Kt qu kho st c th hin trong biu sau:

nh hng ca in tr cc gate n nhit caMOSFET

75 76 7983

87 9197

104

0

20

40

60

80

100

120

Gi tr in tr R201 ()

Nh

itMOSFET(oC)

Series2 75 76 79 83 87 91 97 104

3 5 8 13 18 23 28 33

(e) Nhn xt kt qu th nghim: Kt qu thc t chng minh rng, dng incc gate c quan h mt thit ti t rv tf, do lin quan ti tn tht chuynmch v qua ti nhit ca MOSFET.

Vic xc lp gi tr ti u ca dng cc gate c thc hin qua thcnghim trn c s xc lp mi quan h gia in tr iu khin dng ccgate v nhit lm vic ca MOSFET ch xc lp.

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Gi tr ti u ca dng cc gate t c ti ngng m t vic gimdng cc gate nh hng t ti nhit ca MOSFET.

9. Kt lun

10.Ti liu tham kho

1 Power MOSFET BasicsBy Vrej Barkhordarian, International Rectifier, El Segundo, Ca.

2 THERMAL DESIGN of ELECTRONIC EQUIPMENTJerry C. Whitaker, Technical Press, Morgan Hill, California

3 Testing Guideline for Single Event Gate Rupture (SEGR) of PowerMOSFETsLeif Scheick Jet Propulsion Laboratory Pasadena, California

4 MOSFET Power Losses Calculation Using the Data-Sheet Parametersb y D r . D u a n G r a o v a c , M a r c o P r s c h e l ,Published by Infineon Technologies AG, Am Campeon 1-12, 85579

Neubiberg, Germany5 POWER ELECTRONICS HANDBOOK

ACADEMIC PRESSA Harcourt Science and Technology Company525 B Street, Suite 1900, San Diego, California 92101-4495, USA

6 AN2928 - Application noteModified buck converter for LED applications 2009 STMicroelectronics - All rights reservedSTMicroelectronics group of companies

7 UM0670 - User manual80 W offline LED driver with PFC 2009 STMicroelectronics - All rights reservedSTMicroelectronics group of companies

8 APPLICATION NOTE

DESIGNING A HIGH POWER FACTOR SWITCHING PREREGULATORWITH THE L6560/A TRANSITION MODE I.C.

by G. Comandatore and U. MoriconiSTMicroelectronics GROUP OF COMPANIES

9 L6562TRANSITION-MODE PFC CONTROLLER

STMicroelectronics group of companies

Documents

Report 1 - Research for Thermal of Products